Silica, Diatomaceous

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

Diatomaceous Silica Filter aids of diatomaceous silica have a dry bulk density of 128 to 320 kg/m (8 to 20 Ib/fU), contain paiiicies mostly smaller than 50 [Lm, and produce a cake with porosity in the range of 0.9 (volume of voids/total filter-cake volume). The high porosity (compared with a porosity of 0.38 for randomly packed uniform spheres and 0.2 to 0.3 for a typical filter cake) is indicative of its filter-aid ability Different methods of processing the crude diatomite result in a series of filter aids having a wide range of permeability. 

The filter cake is stirred with 3.1 liters of acetone. The volume of acetone used is about 1.5 times the weight of the cake resulting in about a 65% acetone concentration. The benzoic acid dissolves in the acetone and the urokinase flocculates out. Sodium benzoate, about 1% of the weight of the cake, or 21 grams, is added to speed up the formation of the precipitate. The suspension of crude urokinase in acetone Is filtered on a Buchner funnel using filter paper precoated with a diatomaceous silica product (Celite 505). The precipitate is washed with acetone until the filtrate is water clear. The precipitate is then washed with ether and air dried. The yield of powder so obtained is 2.3 grams. 

Gas chromatography (GC) employs a gaseous mobile phase, known as the carrier gas. In gas-liquid chromatography (GLC) the stationary phase is a liquid held on the surface and in the pores of a nominally inert solid support. By far the most commonly used support is diatomaceous silica, in the form of pink crushed firebrick, white diatomite filter aids or proprietary variants. Typical surface areas of 0.5-4 m2/g give an equivalent film thickness of 0.05-1 pm for normal liquid/support loadings of 5-50 per cent by mass. 

Brand W (2002) Mass spectrometer hardware for analyzing stable isotope ratios. In P de Groot (ed.) Handbook of stable isotope analytical techniques. Elsevier, Amsterdam Brandriss ME, O Neil JR, Edlund MB, Stoermer EF (1998) Oxygen isotope fractionation between diatomaceous silica and water. Geochim Cosmochim Acta 62 1119-1125 Bremner JM, Keeney DR (1966) Determination and isotope ratio analysis of different forms of nitrogen in soils. III. Soil Sci Soc Am Proc 30 577-582 Brenninkmeijer CAM (1993) Measurement of the abundance of CO in the atmosphere and the and 0/ 0 ratio of atmospheric CO with applications in New Zealand and Australia. J Geophys Res 98 10595-10614... 

Synonyms Diatomite diatomaceous silica infusorial earth... 

Procedure Inject 2.5 piL of the Test Preparation into a suitable gas chromatograph equipped with a flame-ionization detector and a 3-m x 2-mm (id) glass column, or equivalent, packed with 3% phenyl methyl silicone (OV-17, Applied Science Laboratories, Inc., or equivalent) on 100- to 120-mesh, silanized, calcined, diatomaceous silica (Gas-Chrom Q, Applied Science, or equivalent). 

Diaminohexanoic Acid Hydrochloride, 229 Diammonium Phosphate, 27, (S3)4 Diastase Activity (Diastatic Power), 793 Diatomaceous Earth, 120, (S2)8 Diatomaceous Silica, 120, (S2)8 Diatomite, 120, (S2)8... 

SYNS AMORPHOUS silica CELITE D.E. DIATOMACEOUS EARTH, NATURAL DIATOMACEOUS SILICA DIATOMITE ... 

The variety of substances used as additives in polymers is considerable. For example, the fillers may include china clay, various forms of calcium carbonate, talc, silicas (diatomaceous silica), silicates, carbon black, etc. The impact modifiers typically include other polymers. Plasticizers include certain polymers with low (oligomers), dialkyl phthalates, dialkyl sebacates, chlorinated paraffin waxes, liquid paraffinic fractions, oil extracts, etc. Heat stabilizers include heavy metals salts such as basic lead carbonate, basic lead sulfate, dibasic lead phosphite (also acting as a light stabilizer), dibasic lead phthalate, stearates, ricinoleates, palmitates and octanoates of cadmium and barium, epoxide resins and oils, amines, diphenylurea, 2-phenylindole, aminocrotonates. The antioxidants include tris-nonyl phenyl phosphite, 2,6-di-ferf-butyl-p-cresol (BHT), octadecyl-3,5-di-terf-butyl-4-hydroxyhydrocinnamate, etc. The UV stabilizers include modified benzophenones and benzotriazoles. Processing lubricants include calcium stearate, stearic acid, lead stearate, various wax derivatives, glyceryl esters and long-chain acids. Fire retardants include antimony oxide, some pyrophosphates, etc. 

Celite, a Johns-Manville registered trademark for a diatomaceous silica product. It is used as a filter aid. Supplier Fisher. Bernstein recommends that a water-washed benzene extract of a reaction product be filtered through a small pad of Celite and evaporated without further drying. 

Celatom [Eagle-Picher]. TM for a group of diatomaceous silicas (diatomite) of high quality and uniformity. 

For amorphous materials, sludges or other poor filtering products, improved filtration characteristics and/or filtrate clarity are enhanced with the use of filter aids. Slurry additives such as diatomaceous silica or perlite (pulverized rock), are employed to aid filtration. Diatomite is a sedimentary rock containing skeletons of unicellular plant organisms (diatoms). These... 

These are prepared from flux-calcined diatomaceous earth, also called diatomite, diatomaceous silica, or kieselguhr. This earth is composed of the skeletons of diatoms, which are single-celled algae. It is excavated from deposits found in various parts of the world. The calcining is carried out by mixing the earth with a little sodium carbonate (called the flux), and raising the temperature to above 900°C. Various white diatomaceous earths are available commercially. The more common of these are Anak-rom U, Celite 545, Chromosorb G (very robust material), Chromosorb W, Gas-Chrom CL, Gas-Chrom P, and Gas-Chrom S. 

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